Electrical heating mat



July 5, 1965 v. R. BEERY ELECTRICAL HEATING MAT Filed Feb. 20. 1961 INVENTOR. VRGIL R. BEERY BY M079 ATTORNEYS FIG. 3

FIG. 2

UnitedStates Patent 3,193,664 ELECTRICAL HEATING MAT Virgil R. Beery, 538 N. Park'St., Centerville, Iowa Filed Feb. 20, 1961, Ser. No. 90,354

7 Claims. (Cl. 219-549) This invention relates to `an electric heating mat and to the method of making the same and, more particularly, it relates to electric heating mats of the type adapted for use in concrete slabs or the like.

In many installations of concrete slabs such as driveways, sidewalks, building floors and roofsor the like, it is desirable to have embedded in the concrete slab an electric heating mat in order to melt snow and ice accumulating on the slab or to keep the temperature of the slab at a desirable level. These heating mats can also be placed in the ground beneath flower beds and in hot houses to provide ground warmth for plants.

One means of producing electric mats for this type use is weaving an electric resistiveheating element through n the opening in a wire mesh, such as chicken wire or the like, and then lay the mat into the concrete when it is poured. y

f This type of rmat, is subject to yseveral disadvantages, one of which is that introducing the electric wire through the openings in a chicken wire orkmesh is a diiiicult and costly operation, and if the electric Wire is sandwiched between two layers of chicken wire or mesh, as is sometimes done, the two outer layers must be fastened together in some way to form an integral mat, Another disadvantage is that during' the weaving, sandwiching or fastening operation, the insulation on the electric wire may become injured and the electric wire shorted to the chicken wire or mesh, making the mat unusable. Also, shorting of the electric heating wire to the chicken wire or mesh maybe inadvertently or accidentally done when the mats are stored, handled or installed.

Further disadvantages are found when these heating mats are used in that current tiowing through the electric resistance wires causes inductive currents to flow in the chicken wire or mesh and, hence, the chicken wire or mesh must be grounded with the result that more electric power is required to produce a given amount of heat.

Therefore, it is an object of the present invention to produce an electric heating mat which is simple in construction, low cost, and one which does not employ a metallic conducting mesh to support the heating wires.

Another object of the present invention is to provide an electric heating mat in which the electric heating wire is supported by a flexible mesh composed of insulating material, such as plastic or the like, with the result that the possibility of the electric heating wire shorting is greatly reduced and there is no necessity for electrically grounding the supporting mesh.

The foregoing and other objects of the present invention are accomplished by providing an electrical heating mat in which an electric heating wire is placed in a desirable pattern on a mesh composed of a flexible insulating material, such as thermoplastic or the like, and then another layer of the insulating mesh is placed on top of the electric heating wire. The composite of the two layers of insulating mesh with the pattern of electric heating wire sandwiched in between is then placed in an oven and heated. During the heating operation, the upper layer and lower layer of the insulating thermoplastic mesh are fused together and the electric heating wire is thus secured integrally with the fused meshes. No pressure is required to fuse the upper layer with the lower layer of the plastic mesh as the weight of the upper layer is sufficient.

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Many other objects and advantages of the present nvention will become'apparent from the following description in conjunction with the drawing in which:

FIG. 1 is a top View of a work area on which an electric heating mat embodying the present invention is kbeing constructed;

FIG. 2 is an enlarged detailed view of the mat of FIG. l; and y f FIG. 3 isa section view of the mat of FIG. 1 taken :along line 3--3 of FIGQZ, but illustrated after heat fusing of the meshes. t

In constructing an electric heating mat 10 as characterized by the features of the present invention, a first layer of an insulating flexible thermoplastic mesh 12 is placed upon the work surface 14. The work surface 14 can be of any size desired, but it has been found that a -four foot width by twenty foot length is sufficient for most size requirements of the mat 10. The mesh 12 `is preferably of diagonal coniiguration and the spacing yand size ofthe strands of the mesh 12 can be varied according to the flexibility, strength and application desired.

Pegs 16 are placed in suitably spaced holes provided in the work surface 14 and then an electric resistance heating wire 18 is positioned on the mesh 12and spaced around the pegs 16 to form parallel lengths, as shown in FIG. 1. As here illustrated, the heating wire 18 is enclosedy in an insulating cover 19 formed of suitable heatresistant, electrical insulating material. The wire 18 can be any suitable resistive heating material, such as niychrome wire, and the size of the wire and spacing can be yadjusted -to suit the given application for the mat 10.

After completing the positioning of the insulating heating wire 18 on the mesh 12 around the spaced pegs 16, a second layer of insulating thermoplastic mesh 20 is placed on top of the heating wire 18 and mesh 12. The mesh 20 is the same type as mesh 12, andthe placement ofmesh 20 doesk not have to be accurately lined up with the voids of mesh 12, but can be more or less at random. The mat 10 is then placed in a heating oven. The heat of the oven and the weight of mesh 20 without other externally applied pressure is sufiicient to cause strands of the thermoplastic meshes 12 and 20 to contact and become fused with each other, thus forming an integral mat with the pattern of heating wire 18 secured loosely between the meshes 12 and2t. The pegs 16 may be removed from the work surface 14 either before or after the heating of the mat. The completed mat 10k is then ready for installation in a concrete drive, sidewalk, building roof or iloor, hot houses, flower beds, or the like. After installation the ends of the heating wire 18 are connected to an electrical power source and the concrete slab or the like is thus electrically heated to the desired ternperature.

The size, resistance, spacing and length of the heating wire 18 can be varied during construction of the heating mats 10 so that the mats can be connected in series or parallel to match the desired voltage source to provide the proper amount of heat desired for any given application. The two layers of flexible plastic mesh 12 and 20 hold the electric heating wire 18 suiiciently in place so that the heating of the slab is substantially uniform and there is no metallic mesh to which the heating wire 18 could become easily shorted during pouring of the concrete.

The method of constructing the mats is simple and economical and the finished mat is light and easy to handle.

Although the present invention has been described with reference to the illustrated embodiment, it should be understood that many other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

g 3,193,664v Patented July 6, 1965` What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electric heating mat comprising an electric heating wire disposed between two layers of flexible thermoplastic mesh fused together.

Z. An electric heating mat comprising an insulated electric resistive heating wire disposed between two layers of flexible thermoplastic diagonal mesh, said layers of mesh being fused together by heating.

3. An electric heating mat of the type adapted for use in heating a concrete slab in which the mat is embedded comprising an insulated electric resistive heating element disposed between two layers of exible thermoplastic material, said material having a plurality of perforations throughout its surface, and said layers being joined together by heating and fusion.

4. An electric heating mat comprising `a continuous electric heating wire having a plurality of parallel lengths disposed in spaced relationship to each other in a common plane, said heating wire being disposed between two layers of exible thermoplastic mesh comprising spaced strands, said strands of a rst layer of mesh being fused together with said strands of a second layer of mesh by heat and weight of said second layer.

5. An electric heating mat comprising :an insulated electric resistive heating wire disposed between two layers of iiexible thermoplastic open mesh, said layers of mesh being fused together by heating.

6. An electric heating mat of the type adapted for use in heating a concrete slab in which the mat is embedded comprising a layer of flexible thermoplastic mesh formed of a plurality of interconnected strands deiining a plurality of voids therebetween, an electric heating wire positioned on said layer crossing a plurality of said strands and extending across a plurality of said voids, and another layer of flexible thermoplastic mesh positioned over said electric heating wire superimposed at random against the first-mentioned layer and formed of a plurality of interconnected strands deiining a plurality of voids, ya plurality of the first-mentioned strands engaging a plurality yof the 4 last-mentioned strands and being fused together at the points of engagement therewith.

7. An electric heating mat of the type adapted for use in heating `a concrete slab in which the mat is embedded comprising a layer of exible thermoplastic mesh formed of a plurality of interconnected strands for embedding in concrete and defining a plurality of voids therebetween for said concrete, and electric heating wire positioned on said layer and having a plurality of runs crossing a plurality of said strands in random fashion and extending at random across a plurality of said voids, and another layer of fiexible thermoplastic mesh positioned over said electric heating wire superimposed at random against the inst-mentioned layer and formed of a plurality of interconnected strands dening a plurality of voids, a plurality of the first-mentioned strands engaging a plurality of the last-mentioned strands between the runs of said heating wire and being fused together at the points of engagement therewith, said heating wire being secured loosely between said layers.

References Cited by the Examiner UNTED STATES PATENTS 1,903,960 4/33 Dreyfus 161-92 2,052,644 9/36 Murphy 219--528 2,333,618 11/43 Strauss 28-73 2,492,397 12/49 Peterson 62-276 2,615,115 10/52 Watter 219-377 2,656,291 10/53 Doll et al. 161-107 2,708,235 5/55 Kaplan 219--219 2,767,113 10/56 Bower 161-137 2,895,535 7/59 Iwao Ono 156--380 2,932,711 4/60 Adams 219-345 2,943,289 6/60 Colten et al. 219-538 X 2,974,566 3/61 Hurley 15G-275 X 2,977,270 3/61 Bodle 156-270 FOREIGN PATENTS 836,555 6/60 Great Britain. 1,154,998 11/57 France.

OTHER REFERENCES British Plastics, page 3l, January 1958.

RICHARD M. WOOD, Primary Examiner.

MAX L. LEVY, Examiner. 

1. AN ELECTRIC HEATING MAT COMPRISING AN ELECTRIC HEATING WIRE DISPOSED BETWEEN TWO LAYERS OF FLEXIBLE THERMOPLASTIC MESH FUSED TOGETHER. 